I strongly believe that there are only two true rules when it comes to presentations: (1) know who your audience is, and (2) tell something that the audience will find useful. Not eloquent, cute, clever, or impressive; but useful (to them).

All these theories, rules, and advice about giving presentations are just useless fads that are often impractical and unnatural for most people.

People often confuse an eloquent and natural speaker with having a "good" presentation. I have been to many talks (Tufte, for example) where the presenter talks smoothly for an hour, yet in the end does not say anything useful to me. Your are entertained, in a sense, but you don't actually learn anything.

To many presenters, the presentation is actually about themselves rather then giving something truly useful to the audience. A lot of people can talk well, but I rather have somebody that can teach me something, even if the delivery is not perfect.